Events leading to the onset of various ocular complications are being investigated. Specific studies include the role of enzymes aldose reductase and aldehyde reductase in the onset and progression of retinopathy, cataract, keratopathy, pupil function changes, and iris and ciliary process structure changes associated with diabetes and galactosemia. In addition, methods for either delaying or preventing the onset and progression of these complications through the pharmacological control of these enzymes are being developed. Also being studied are events leading to the formation of several types of cataracts, as well as methods for controlling the onset of these cataracts through pharmacological intervention.